Stabilization of polyiodide networks with Cu(ii) complexes of small methylated polyazacyclophanes: shifting directional control from H-bonds to I⋯I interactions

Abstract

Ordered polyiodide networks have recently gathered considerable attention as electronic materials, a topic historically dominated by metals. Could we incorporate metal cations into polyiodide frameworks in a controlled manner to simultaneously boost electronic properties and robustness of these materials? Herein we present a first principles study featuring three analogous polyazacyclophanes (L, L-Me, L-Me₃), differing only in the extent of N-methylation. We demonstrate (potentiometry, ITC) how they all form the same CuL²⁺ (L = L, L-Me, L-Me₃) complex as prevalent species in solution, so that a level playing field exists where only N-methylation distinguishes them. Then we use them as countercations for polyiodide growth. XRD analysis of the resulting crystals clearly shows that methylation is a valuable tool to gradually shift directional control of subtending pairing preferences from H-bond to I⋯I interactions: this affects global packing and actively incorporates metal centres into polyiodide chains, setting the scene for further developments.